Astronomy

How is it possible that the CMB approaches the earth from all directions?

How is it possible that the CMB approaches the earth from all directions?

I presume that the photons from the CMB approach the earth from all directions, otherwise we couldn't detect them with a picture where it is present everywhere in the universe with a tiny anisotropy.

Now the CMB is a result of the big bang. Another result of the big bang is that in all directions we see galaxies moving away from us, like we are in the center of the universe (which is probably not the case).

But why are all the galaxies (except a few) moving away from us while the CMB is approching us. What is the reason for that difference? Or aren't those photons coming from everywhere?


You are comparing apples and oranges. The CMB is like the light from a distant galaxy, which while the galaxy is receding the light approaches us. CMB is the light emitted by universe at recombination. The matter that emitted the CMB is/was receding from us with a very high red-shift.


The Big Bang happened everywhere and the recombination of electrons with nuclei - the thing that causes the CMB - also happened everywhere. So in every direction you look you can see the radiation from that recombination.

But that recombination also happened a long time ago and so, given light has a constant velocity, the places where we can see the recombination take place are also a long way away. And, as a result of the expansion of space-time, that radiation is very red-shifted, so instead of the recombination looking like it is happening at roughly 4000 degrees Kelvin, it looks like something happening at 3 degrees Kelvin.

That expansion is also what makes it look like the distant galaxies are all moving away from us and the further away the faster they seem to be moving.


History of the Big Bang theory

The history of the Big Bang theory began with the Big Bang's development from observations and theoretical considerations. Much of the theoretical work in cosmology now involves extensions and refinements to the basic Big Bang model. The theory itself was originally formalised by Belgian Catholic priest, mathematician, astronomer, and professor of physics Georges Lemaître.


Doubt about the relativity of simultaneity

(I hope my English is understood). Hello, I have a question regarding the relativity of simultaneity.

The mean temperature of the cosmic microwave background tells us how big the universe is with respect to the recombination epoch. If I now measure that the mean temperature of the cosmic microwave background is 3 Kelvin, and I know that at the time of recombination it was 3000 Kelvin, then I can deduce that the universe is now (3000/3 = 1000) 1000 times more larger than in the recombination era. From then until now the universe has been expanding to multiply by 1000 its size.

The mean temperature of the cosmic microwave background is the same for two observers who measure it simultaneously, regardless of their relative motion. Two observers with relative movement between them, by Doppler effect, may not agree on the temperature of the cosmic microwave background in a certain direction, but if they both make the measurements simultaneously, they will both measure the same mean temperature of the cosmic microwave background.

And this is problematic. Let me explain, let's imagine two radio telescopes with no relative motion between them, radio telescope 1 and radio telescope 2. Both radio telescopes can measure the mean temperature of the cosmic microwave background with great precision. Radio telescopes are turned on by hitting their switch with a beam of light.

Right in the center is a light source, with no relative motion relative to radio telescopes. The light source sends a beam of light to each radio telescope, hits the switch, turns them on. Both radio telescopes measure the mean temperature of the cosmic microwave background. It turns out that both radio telescopes get exactly the same result.

Observer A is not moving relative to the system. From the reference frame of observer A, the light rays reach both radio telescopes at the same time. Therefore observer A sees that both radio telescopes are turned on at the same time. Observer A is told that both radio telescopes measured exactly the same mean temperature of the cosmic microwave background. Since observer A saw that both radio telescopes measured the mean temperature of the cosmic microwave background at the same time, he understands that the data agrees with his observation.

Observer B does move relative to the system. From the reference frame of observer B, first a ray of light arrives at radio telescope 1, and then a ray of light arrives at radio telescope 2. Therefore observer B sees that radio telescope 1 turns on first and radio telescope 2 later. Observer B is told that both radio telescopes measured exactly the same mean temperature of the cosmic microwave background. Observer B understands that there is a conflict between his observations and the measurements from the radio telescopes.

Since from the reference frame of observer B, radio telescope 1 is turned on first and then radio telescope 2, observer B expects that the measurement of the mean temperature of the cosmic microwave background of radio telescope 1 is higher than that of radio telescope 2. Without However this does not happen, both measures are identical.

Then observer B reaches the following conclusion:
-Or for a certain period of time, from its reference frame, the universe stopped expanding.
-Or the simultaneity is not relative, but absolute.


How is it possible that the CMB approaches the earth from all directions? - Astronomy

I will be going to Oslo this June. I understand that, north of some specific latitude, the sun does not set at all for one or more nights. What path does the sun follow during this time? I've heard it described as tracing a small halo over the northernmost point in the sky, never dipping below the horizon as it retrogrades back to its starting point in the circle. Is this even close?

The "critical" latitude is 66.5 degrees. But Oslo is only at 60 degrees and so you should not be seeing the "midnight sun" there.

The path of the Sun depends on the latitude of the place. At the latitude of 66.5 degrees north, the Sun will not set on June 21. On this day, the Sun rises at north, goes towards east reaching higher portions of the sky reaching a maximum elevation of about 47 degrees above the horizon at south, then go towards west and just touch the horizon (without setting) at north. Thus, the Sun never sets and goes in a circle in the sky. Now consider the extreme case of the north pole. There, the Sun will be tracing circles of roughly constant elevation for months!

Also, this year boasts a full moon on June 24. I'm intrigued by the thought of a full moon and the sun in the sky at the same time, and I was hoping to take a photograph of something I may never see again. My question: I assume the sun will be at its westernmost point in the sky when the moon rises in the east, and they will travel in opposite directions until the sun is in the east as the moon sets. How close in terms of degrees will they approach each other? That is, if the moon were directly overhead when the sun is due north touching the horizon, they would be 90 degrees apart, and I would need a pretty wide lens. Is this close to the truth?

You will almost never see the full moon and the Sun at the same time. The reason for this is that all the planets, Moon and the Sun lie in a plane in the sky called the ecliptic and this plane is tilted to the Earth's equator by about 23.5 degrees. On full moon day, the Moon and the Sun are roughly (not exactly) on opposite sides of Earth. Hence, if the Sun is at a declination of 23.5 degrees (which it will be close to summer) in the constellation of Gemini, then the Moon will be at a declination of -23.5 degrees in the constellation of Sagittarius.

Places on the Earth north of 66.5 degrees will never see the part of the ecliptic that is in Sagittarius (even though some parts of the constellation that are above the declination of -23.5 degrees may be seen depending on the latitude of the place). Hence, if you are at a latitude of say 80 degrees, the Sun will be above the sky all day during summer and the Moon will never rise during full moon.

However, the Moon's orbit is inclined to the ecliptic by about 5 degrees which is the reason why we do not see a solar eclipse during every new moon. Hence at latitudes close to 66.5 degrees, one might be able to see the Sun and the full moon for a very short time simultaneously if the geometry of the Moon is just right. However, the Sun and the full moon will be on opposite portions of the sky and so nobody will be able to photograph it unless there is an exceptional camera that can take a picture of the entire sky.

In Oslo, you will find a normal moonrise during full moon. The Sun will be up for a very long time and the full moon will rise shortly after sunset. Soon after moonrise, the Moon will set again and then the Sun will again rise. For the very same reason that you have the Sun for almost 24 hours, you will have the full moon in the sky for a very short time only.

This page was last updated on July 18, 2015.

About the Author

Jagadheep D. Pandian

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.


Notion of the distances and the space

The astronomy works on a scale of distance that the man has difficulty in representing himself. So, the astrophysicists use the speed of light as standard measuring apparatus. Indeed, knowing that the light moves in 300 000 km/s in the space (the fastest existing speed in relativist physical appearance), when a time is indicated in speed-light, it is necessary makes understand a distance.
To approach the astronomy it is necessary to have first of all a notion of the distances and the space which separates celestial bodies. Then it is necessary to have a notion of the masses in presence. To give an image of the distances which separate the celestial bodies of our solar system, here is a model with a scale in 1/100 billionth, (1cm = 1 million km).

With this scale the solar system likes in the Big Stadium of France. The Sun, in the center of the stadium, would be 1,4 cm one diameter.
In 1,5 m of distance would be the Earth with a diameter of 0,1mm, Jupiter would be in 8m of the sun and would measure 1,4mm. Pluto would be in 59m of the Sun and would be one diameter of 0,05mm. The closest star Alpha Centauri C Proxima Centauri (so sometimes called Alpha Centauri C) is a red dwarf of visible magnitude 11 too weak to be visible in the bare eye, situated in the constellation of the Centaur. It is one of three stars that form the Alpha Centauri system. It is the star the closest to the solar system in 4,22 years light. in neighborhood of Barcelona and Sirius (the same size as the Sun) would be in neighborhood of Lyon and.

Image: The speed of light is fixed to 299 792 458 m/s in 1983 by the weights and the measures, is a constant physics from which a precise value is obtained experimentally from the XVII th century by the Danish astronomer Ole Christensen Romer in 1676. The speed of light was then esteemed at 200 000 kilometers per second, approximately 35 % below its true value because of the uncertainties of time on the size of the orbit of the Earth. However, Cassini emitted doubts on the validity of the results of his colleague. James Bradley proposed then an estimation in km/s 300 000. Today, the speed of light constitutes one of the pillars of the theoretical physics.


How is it possible that the CMB approaches the earth from all directions? - Astronomy

I will be going to Oslo this June. I understand that, north of some specific latitude, the sun does not set at all for one or more nights. What path does the sun follow during this time? I've heard it described as tracing a small halo over the northernmost point in the sky, never dipping below the horizon as it retrogrades back to its starting point in the circle. Is this even close?

The "critical" latitude is 66.5 degrees. But Oslo is only at 60 degrees and so you should not be seeing the "midnight sun" there.

The path of the Sun depends on the latitude of the place. At the latitude of 66.5 degrees north, the Sun will not set on June 21. On this day, the Sun rises at north, goes towards east reaching higher portions of the sky reaching a maximum elevation of about 47 degrees above the horizon at south, then go towards west and just touch the horizon (without setting) at north. Thus, the Sun never sets and goes in a circle in the sky. Now consider the extreme case of the north pole. There, the Sun will be tracing circles of roughly constant elevation for months!

Also, this year boasts a full moon on June 24. I'm intrigued by the thought of a full moon and the sun in the sky at the same time, and I was hoping to take a photograph of something I may never see again. My question: I assume the sun will be at its westernmost point in the sky when the moon rises in the east, and they will travel in opposite directions until the sun is in the east as the moon sets. How close in terms of degrees will they approach each other? That is, if the moon were directly overhead when the sun is due north touching the horizon, they would be 90 degrees apart, and I would need a pretty wide lens. Is this close to the truth?

You will almost never see the full moon and the Sun at the same time. The reason for this is that all the planets, Moon and the Sun lie in a plane in the sky called the ecliptic and this plane is tilted to the Earth's equator by about 23.5 degrees. On full moon day, the Moon and the Sun are roughly (not exactly) on opposite sides of Earth. Hence, if the Sun is at a declination of 23.5 degrees (which it will be close to summer) in the constellation of Gemini, then the Moon will be at a declination of -23.5 degrees in the constellation of Sagittarius.

Places on the Earth north of 66.5 degrees will never see the part of the ecliptic that is in Sagittarius (even though some parts of the constellation that are above the declination of -23.5 degrees may be seen depending on the latitude of the place). Hence, if you are at a latitude of say 80 degrees, the Sun will be above the sky all day during summer and the Moon will never rise during full moon.

However, the Moon's orbit is inclined to the ecliptic by about 5 degrees which is the reason why we do not see a solar eclipse during every new moon. Hence at latitudes close to 66.5 degrees, one might be able to see the Sun and the full moon for a very short time simultaneously if the geometry of the Moon is just right. However, the Sun and the full moon will be on opposite portions of the sky and so nobody will be able to photograph it unless there is an exceptional camera that can take a picture of the entire sky.

In Oslo, you will find a normal moonrise during full moon. The Sun will be up for a very long time and the full moon will rise shortly after sunset. Soon after moonrise, the Moon will set again and then the Sun will again rise. For the very same reason that you have the Sun for almost 24 hours, you will have the full moon in the sky for a very short time only.

This page was last updated on July 18, 2015.

About the Author

Jagadheep D. Pandian

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked at the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the Indian Institute of Space Scence and Technology.


A Big Bang – Part 1

How did the universe begin? In almost all public schools and universities, the most commonly promoted idea of universal origins is the big bang. The idea is that the universe began billions of years ago as a point of infinitesimal size which sprang from nothing and began expanding. Energy became matter which then became stars, galaxies, and planets. Is the big bang really a reasonable theory about how the universe began? Can it be reconciled with Scripture? Is it based on good science?

What is the Big Bang?

Invented by Georges Lemaître in 1931, the big bang is a conjecture about the very early universe. In the 1920s Edwin Hubble and others found a relationship between the measured redshift and distance of galaxies. Redshift is a phenomenon whereby the light of an object is displaced in frequency toward longer wavelengths from its laboratory frequency. The easiest way to cause redshift is for the object emitting the light to be moving away at high speed from the observer. Hubble found that distant galaxies had higher redshifts than nearby galaxies. This observation is consistent with what we would expect if the entire universe were expanding.

Lemaître was quite familiar with general relativity – the branch of physics discovered by Albert Einstein. He found that Einstein’s equations implied that the universe cannot be static, but must either be expanding or contracting. He learned of Hubble’s observations that implied an expanding universe. And these observations seemed to confirm his own theoretical predictions. The universe is indeed expanding. In 1927, Lemaître published his conclusion that the universe was expanding. He even made an estimate of the expansion rate, which today we call the Hubble constant. Although this early estimate of the Hubble constant was not very accurate due to the observational limitations of that era, the basic reasoning was brilliant. Most creation astronomers today agree that the universe is expanding as predicted on the basis of Einstein’s field equations along with observations of redshifts. This is sensible science, repeatable and testable in the present.

However, in 1931, Lemaître published a paper in which he speculated on how the expansion of the universe began. This goes beyond the limits of science because we cannot test or repeat what supposedly happened in the distant past. Lemaître’s conjecture was based on an extrapolation. He took the current expansion rate of the universe along with the assumptions of uniformitarianism (that the expansion rate has been consistent over time) and naturalism (that God had not supernaturally created the universe), and inferred that the universe has always been expanding since it began as a point of no size – a primeval atom. Over time the idea came to be called the big bang, or the standard model. The uniformitarian assumption is questionable of course. But naturalism is something that any Christian should reject as false because naturalism denies the supernatural.

Interestingly, Lemaître professed faith in God. He was an ordained Roman Catholic priest. He apparently rejected the literal history of Genesis, and believed that science and faith were separate issues and that one had nothing in common with the other. Hence, he embraced methodological naturalism. Methodological naturalism is a softer version of naturalism, which accepts that the supernatural might happen, but that when we are doing science, we must pretend that the supernatural does not happen.

In essence, the methodological naturalist does science as if he were an atheist, though he might not actually be an atheist. It is a strange position. The methodological naturalist acknowledges that God does or might exist, but does science on the assumption that God does not exist. Is it rational to do science from an assumption that is definitely (or at least possibly) wrong? If a person’s reasoning is based on a false premise, is there any reason to trust the conclusion? Yet, it is surprising how many professing Christians hold to methodological naturalism.

Given that Lemaître built his hypothesis on two unbiblical assumptions, we should be very skeptical of his conclusions. Nonetheless, it is theoretically possible for a person to draw a correct conclusion by accident from faulty assumptions or faulty reasoning. So is it possible that Lemaître’s idea of a big bang could be true? Could the big bang be the mechanism that God used to create the universe? Is the big bang / standard model compatible with the history of creation presented in the Bible?

Biblical Considerations

In fact, there are many contradictions between the big bang and the Bible. The first incompatibility is the timescale. In the current version of the big bang, the universe supposedly came into existence about 13.8 billion years ago. The Bible states that God created in six days, each bounded by one evening and one morning, which forms the basis of our work week (Genesis 1, Exodus 20:8-11). Furthermore, Adam was created on the sixth day, and from the ages given in Scripture, we know this was a few thousand years ago. An exact date is not needed in order for us to know that 13.8 billion years is far older than what the Bible allows – by a factor of about 2 million. This is hardly a negligible difference. If the height of an average man represented the biblical timescale, then the big bang timescale would be about the width of the United States.

Some people have the impression that if they could just stretch the days of creation into vast ages, this would allow the Bible to be compatible with the big bang. Of course, the language of Genesis is very clear and cannot be stretched to accommodate deep time. Nonetheless, it would not resolve the disparity anyway because the order of events differs. The Bible teaches that stars were created on day 4 of the creation week, whereas Earth was created on day 1 (Genesis 1:1, 14-19). However, in the standard model, stars formed billions of years before the Earth. In fact, the standard model supposes that terrestrial planets like Earth formed from elements forged in the core of stars.

The creation of stars after the Earth is so contrary to the big bang that some Christians have asked, “Couldn’t Genesis simply mean that the stars appeared on day 4, rather than being made on that day?” The answer is: no. The Hebrew text teaches that God made (using the Hebrew word asah) the lights in the firmament on the fourth day – not that He made them appear, which would be a different Hebrew word (ra’ah). Could it be merely the sun and moon that were made on the fourth day? No. The Hebrew language has a preposition (‘et) (which has no parallel in English) that marks the direct object of the verb. This word is used in Genesis 1:16-18 to mark the stars as the object that God made. The text therefore specifies that the stars are the objects that God made on the fourth day (along with the sun and moon).

And there are other order differences. According to the Bible, Earth was created before light (Genesis 1:1,3). However, in the big bang model, light existed billions of years before the Earth formed. The Bible states that liquid water existed before stars (Genesis 1:2, 14-19). But in the big bang view, the oxygen in every water molecule was supposedly produced in stars. In the standard model, the Earth had no water to begin with, but began as magma.

The Mechanism

So the timescale and order of events of the big bang contradict those of the Bible. The big bang therefore cannot be true if the Bible is and the Bible cannot be true if the big bang is. But there are additional differences. A significant difference concerns the mechanism by which space, time, stars, and planets were made. The big bang is a naturalistic model. Advocates believe that natural laws can account for the origin of the universe and all the objects within it. God is neither desired nor required. Indeed, the whole point of the big bang is to explain how the universe and its features came to be without invoking the supernatural.

But doesn’t the Bible teach that God supernaturally created the heavens and the Earth? To answer this question, we need to define our terms. Unbelievers tend to have the common misconception that the word “natural” means that God is not involved, whereas “supernatural” is when God intervenes. However, the Bible teaches that God upholds the entire universe by the expression of His power (Hebrews 1:3) and accomplishes all His good pleasure (Isaiah 46:10). So everything that happens in this universe is ultimately enabled by God’s power. Natural phenomena demonstrate God’s power just as much as supernatural phenomena. They are equally demonstrations of God’s omnipotence.

What then is the difference? ‘Natural’ refers to the normal, consistent, repeatable way that God upholds the universe, and ‘supernatural’ refers to an unusual, extraordinary manifestation of God’s power. Consider the orbits of the planets around the sun. What keeps them from flying off into space? Ultimately, the planets orbit by the will of God, yet most physicists would say that the sun’s gravity keeps them tethered. The two answers are perfectly consistent when we recognize that gravity is merely the name we give to the way that God keeps the planets in orbit. Gravity is not a replacement for God’s power, but an example of God’s power. And since gravity is the normal, repeatable way that God accomplishes his plan, this falls under the category of natural law. Anything that happens normally, repeatedly, or predictably is a natural manifestation of God’s power, rather than a supernatural manifestation.

So was the creation of the universe natural or supernatural? During the creation week, God was speaking into existence things that had no previous existence. He created the Earth. He created plants, animals, and people with no ancestors. These are not things that God continues to do today. They are not repeated throughout time, and are therefore supernatural. Genesis 2:2 confirms that God is not doing the acts of creation today that He did during the creation week. This verse states that by the seventh day God completed/ended His work (of creation). Since God is not doing today what He did during the creation week, we can say for certain that the creation week involved supernatural manifestations of God’s power. The creation of the universe, the celestial luminaries, the Earth, and life on Earth therefore cannot be correctly described by a naturalistic model. The naturalistic mechanism of the big bang is fundamentally wrong because it assumes that the universe formed in the same way it is upheld today.

The origin of the universe was not a violent, naturalistic “bang.” It was an orderly sequence of objects being supernaturally created as the Lord spoke them into existence.

The standard model is not only a story about the past it is also a story about the future. There were originally three versions of the future of the universe allowable within the big bang model. But recent observations have essentially eliminated all but the following position. According to the standard model, the universe will continue to expand forever. Energy will continue to convert from a usable to an unusable form. After eons of time, all usable energy will be gone. In this “heat death” stars will no longer exist, and life will not be possible. The universe will be nothing more than low-energy radiation and black holes.

It is a rather bleak view, and one that contradicts the future described in the Bible. The Bible teaches that there will be a future judgment and restoration. The new heaven and new Earth will last forever, and those who have received Christ as Lord will live forever with Him. What is perplexing is that many Christians reject the biblical view of origins in favor of the big bang, while they accept the biblical view of the future while rejecting the big bang’s future. This is dreadfully inconsistent. If we cannot trust that God got the details right in Genesis, then why trust that He got the details right on the future? Some people might object that the future judgment and restoration are supernatural actions by God, and hence a naturalistic model is insufficient to describe or evaluate them. But then again, the Bible teaches that the creation of heaven, earth, and whatever is in them was a supernatural sequence of events. Hence a naturalistic model is insufficient to describe them.

A Beginning

Strangely, some Christians have claimed that the big bang is biblical on the basis that it teaches that the universe had a beginning, just as the Bible does. Of course, the Lord of the Rings trilogy also has a beginning. Should we therefore believe that the Lord of the Rings is an accurate description of origins and compatible with the Bible? Clearly, one point of agreement does not undo the many differences between biblical origins and the big bang story. Ultimately, the big bang and the Bible give two very different descriptions of the origin of the universe, and acceptance of one therefore logically requires rejection of the other.

The history of secular thinking on origins may shed some light on this issue. In the mid-twentieth century, there were two main secular models of the origin of the universe: the big bang and the steady state model. Both embraced an expanding universe. But the big bang assumed that this expansion began from a point billions of years ago, whereas the steady state assumed that the universe was eternal, infinite in size, and has always been expanding. Since expansion would naturally lead to a drop in density, the steady state theory proposed that new matter constantly forms from nothing in the void to keep the average density of the universe constant.

Both models were equally consistent with the observations, until 1964. Since the big bang begins with all the energy in the universe concentrated into a point of no size, when the universe first starts to expand, the energy density would be incomprehensibly high. This corresponds to an extremely high temperature, which would produce electromagnetic radiation (light of very high frequency). As the universe expanded, this light would drop in frequency as its wavelengths stretch along with space. In 1964, Arno Penzias and Robert Wilson discovered that low-energy microwaves were traveling through space from apparently all directions: a cosmic microwave background (CMB). Many astronomers immediately assumed that these microwaves were the stretched-out leftover radiation produced in the big bang. Since the steady state model did not predict such radiation, the discovery of the cosmic microwave background was hailed as the proof of the big bang and the refutation of the steady state model.

But there are two significant problems with this reasoning. First, we note that the biblical model was not invited to this competition. Only the two most popular naturalistic models were considered – a bifurcation fallacy. We can easily “prove” something that is false by considering only wrong options. Consider incorrect option A or incorrect option B. Incorrect option B doesn’t fit the observations, therefore A. But what about option C? After all, the Bible also teaches that there was light before stars (Genesis 1:3, 16-18), and seems to imply an expanding universe (Isaiah 40:22). So we might reasonably expect to find microwaves throughout space on the basis of Scripture as well.[1]

Second, although the steady state model did not predict a cosmic microwave background, no one at the time seems to have considered whether or not it should have made such a prediction. In any universe that has matter with non-zero energy, that matter must radiate electromagnetic energy. Some places will naturally be warmer than others. But over time, the universe will be flooded with radiation corresponding to its average temperature. At an average temperature of 2.7 degrees above absolute zero, the radiation will have the frequency of microwaves. The point is that the existence of a cosmic microwave background is not a unique feature or the big bang model any universe with an average temperature will eventually have a CMB.

The big bang was invented to explain the origin of the universe and its features without God. It is a naturalistic model and is incompatible with the Bible. The big bang differs with the biblical account on the timescale, the order of events, the mechanism, and the future. Therefore, for those who believe the Bible, the big bang is not an option. What remains to be considered are the scientific merits of the big bang. If we did not have the Bible, if we did not know the true origins of the universe, would the big bang be a reasonable scientific hypothesis? More to come.

[1] I am not suggesting that this is definitely the explanation of the cosmic microwave background – only that it is a possibility.


Seeing a black hole with millimetre waves

Another terahertz astrophysical project required far higher resolution than Planck attained. In April 2019 the international Event Horizon Telescope (EHT) collaboration presented the first ever image of a black hole – the supermassive black hole at the centre of the elliptical galaxy M87, 55 million light-years away.

The aim had been to study the region near the event horizon by observing the black hole’s “shadow”, a dark area within the glow emitted by hot accretion material flowing into the black hole. The shadow, caused by the gravitational bending and capture of light near the event horizon, has a diameter about five times the Schwarzschild radius (the radius of the black hole) as predicted by general relativity. It would subtend only a tiny angle of

Terahertz photons delineate a black hole because they come from deep within its gravitational well. Earlier studies of M87 at wavelengths from 1.3 mm to 7 mm had shown signs of a central 40 μ arcsec structure but could not image it. These results did, however, show that the shorter the millimetre wavelength, the more closely the photons represented the actual site of the black hole within the bright region. But no individual radio telescope installation, single-dish or multi-dish, could provide the required angular resolution at millimetre wavelengths.

The answer was for the EHT to link eight separate installations around the Earth, including the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean desert, the South Pole Telescope (SPT) in Antarctica, and the IRAM 30-metre telescope in Spain (figure 3). The resulting virtual telescope gave an angular resolution of the order of the 1.3 mm wavelength divided by the Earth’s diameter. After an intricate process of co-ordinating the telescopes and analysing petabytes of data, the composite network produced a striking image at a resolution of 20 μ arcsec. It clearly shows the dark shadow within the bright emission region 42 μ arcsec across, which itself displays details. Analysis of the data gave a central mass of 6.5 × 10 9 solar masses, definitively establishing the existence of a supermassive black hole in M87 and supporting the supposition that black holes of this size lie at the centre of galaxies.


6. Reionization Distortions With Anisotropy Measures

The effect of peculiar velocity on the frequency spectrum at each desired observational frequency can be evaluated on the whole sky using the complete description of the Compton-Getting effect (Forman, 1970). To this aim, we can simulate the corresponding maps on the basis of the Lorentz-invariance of the distribution function, including all orders of the effect and their link with the geometrical properties induced at each multipole. We review here the fundamental concepts and the observational perspectives opened by the next generation of CMB anisotropy missions including realistic simulations of foreground and calibration limitations.

We first discuss the dipole spectrum frequency dependence (Danese and de Zotti, 1981 Balashev et al., 2015). The 𠇍ipole amplitude is directly proportional to the first derivative of the photon occupation number, η(ν), which is related to the thermodynamic temperature, Ttherm(ν), i.e., to the temperature of the blackbody having the same η(ν) at the frequency ν, by ” Burigana et al. (2018)

The difference in Ttherm measured in the direction of motion and in the perpendicular direction is given by Danese and de Zotti (1981):


Why is the C.M.B. visible in every direction?

If it is the case that the big bang was a local event how is it that the cosmic microwave background is visible from every spacial angle?

If there was superluminal expansion, surely only one direction should have the remnants.

If the photons escaped the plasma during expansion, surely there was nothing for them to scatter off of -- back towards us -- and we shouldn't see anything.

Is it topological? Something like a 4-D stereographic projection where the projection point is the big bang such that all 3-D spacial paths trace a meridian back into the past?

How can we even tell that it's the big bang and not radiation from non-observable universe beyond our small bubble?

If it is the case that the big bang was a local event

This is not the case. The big bang happened everywhere simultaneously. It was not like an explosion with forces acting to drive matter outward into pre-existing empty space. It was more like the inflation of a half-inflated balloon -- if you were to draw a grid on the balloon and inflate it, all points on the grid would expand away from all other points on the grid, and not due to any forces acting along the grid lines.

how is it that the cosmic microwave background is visible from every spacial angle?

Because it was emitted from all regions, in all directions. All the light that was emitted from everywhere 13.7 billion years ago is finally reaching us now from every direction.

Is it topological? Something like a 4-D stereographic projection where the projection point is the big bang such that all 3-D spacial paths trace a meridian back into the past?

It's not even that. The balloon analogy I used above is actually flawed in precisely this way -- the surface of a balloon is 2-dimensional but an actual balloon is 3-dimensional, so with a balloon, you can imagine a "center" that exists but just isn't on the surface, and is in some hidden dimension. If you take that analogy you would expect this means our 3-dimensional space must be embedded in a 4-dimensional space where the center of the big bang is actually somewhere else in that 4th dimension.

But that's not the case either. The way the mathematics work, there is no need for there to be a 4th spatial dimension in which our universe is embedded. A better analogy that would capture this is like if our universe were an infinite 3D sponge, the kitchen sink kind of sponge, but infinite in all directions. It started out in a squeezed state, and expanded uniformly as it relaxed. It was already infinite prior to the expansion, and it is still equally infinite as it relaxes . but nevertheless, any two given points in the sponge are now further away from each other than they were when the sponge was squeezed. This example better captures the expansion without needing any embedding in a fourth dimension.

Edit: Another way to think about it is: if "everything is expanding away from this point" is the qualifier for the center, then every point is equally qualified to be the center, because everything is expanding away from everything else.

How can we even tell that it's the big bang and not radiation from non-observable universe beyond our small bubble?

One big giveaway is that the big bang model actually predicted both the existence and the spectrum of this light, and the scale of its small anisotropies, all long before it had been experimentally observed. When you make such a stupidly-specific prediction that no other model makes, and then finally go looking and find out that nature almost perfectly matches the prediction . well, you know .

Another aspect is that the CMB is extremely uniform, suggesting that all the distant regions at the edges of our observable universe were likely all in causal contact at one point in time (indicating it was very likely much closer together in the past, and was driven out of causal contact by an inflationary mechanism).

We also know that beyond a certain scale, the universe becomes observably uniform and no new large-scale structures exist beyond that given size -- this feature is called the End of Greatness, so we would expect the same kinds of matter to be at the edge of the observable universe and beyond that edge, as there is in nearby regions to us.


Watch the video: How is it possible? - 11 incredible Balance Tricks (December 2021).