Brief Answer: 

All the scientific evidence available supports the conclusion the Universe had a beginning.

Reference: New Scientist, “Why physicists can’t avoid a creation event”, January 11, 2012, Cosmologist from Tufts University, A. Vilenkin, stated: “All the evidence we have says that the universe had a beginning.”

Renown cosmologist Alexander Vilenkin concludes: “It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape: they have to face the problem of a cosmic beginning.” (Vilenkin, Many Worlds in One, 176)

Detailed Answer:

When Albert Einstein was working on the field equations for his general theory of relativity, it seemed the equations were pointing to the necessity of space to either be expanding or contracting, and if it was expanding, then going backwards in time would lead to the universe collapsing into a beginning point. Einstein rejected this idea, believing our Universe had no beginning, but was later invited to visit astronomer Edwin Hubble, whom the Hubble telescope is named after, as Hubble noticed galaxies were moving away from each other.

Have you ever noticed the sound of an approaching train or car changes as it passes, and then moves away from you? This change in the sound waves is known as the Doppler shift. Imagine having a coil, with one end held by someone on the train, and the other end held by you. As the train approaches you, the coil compresses, and when the train passes you and moves away the coil stretches out. When something moving towards you gives off a sound wave, the wave gets compressed, which changes the wavelength or pitch of the sound, when the source of the sound passes and moves away from you, the sound stretches into a new pitch. Light waves have the same compression or stretching, and instead of changing in sound pitch, light waves change in color, depending if the source of the light is moving towards or away from you.

Edwin Hubble noticed the light waves coming to us from every galaxy[1] in space were being stretched out, causing the light waves to have a “red shift”. If light is getting stretched into the red end of the light spectrum, it means the galaxies are all moving away from us, the universe is spreading apart. This supports Einstein’s discovery that if we could go back in time, then the universe would shrink down to smaller and smaller volume, and when small enough gravity would take over and compress the universe into even smaller volume, eventually reaching a beginning point.

Later, the Penrose-Hawking singularity theorems explained how the unfathomable gravity of the universe being so condensed at the beginning would bend space-time so much, there would be a singularity, which leaves no space for nature to exist. There would be no place for nature, space or time to exist. Nature had to be created from “nothing”, at least, from nothing of the matter, energy, space and time of nature—because all of nature is what came into existence.

If the universe came into existence, the light and heat leftover after such a beginning event would cool over time, and this temperature could be calculated and detectable in every direction in space. Astronomers Arno Penzias and Robert Wilson of Bell Labs were testing an enormous antenna by measuring signals from space, and discovered a uniform signal in every direction. In attempting to determine what this signal was, they even considered pigeon droppings on the antenna, but eventually found they were the first to discover the CMB, which was at the predicted temperature just above absolute zero. Penzias and Wilson received the Nobel Prize in Physics and confirmed the leftover radiation of a creation event.(Arno A. Penzias and Robert W. Wilson, “A Measurement of Excess Antenna Temper­ature at 4080 Mc/s,” Astrophysical Journal 142 (July 1965): 419–421, doi:10.1086/148307)

From Einstein, Hawking and multiple Nobel prize winners, there are many sources of evidence confirming the Universe had a beginning: such as the cosmic microwave background (CMB) radiation, theory of relativity, percentage of light and heavy elements present in the universe, Hubble’s red-shift of galaxies, “ripples” of the Big Bang, etc. Bottom-line: ALL of the evidence we have supports the Universe had a beginning, and came into being not from anything of the Universe or nature as nature is what began to exist at that moment. Many picture the Big Bang starting within an already existing universe, or a vacuum, or a small point with empty space around it, but this is not accurate.

As stated by John Barrow and Frank Tipler, both mathematical physicists and cosmologists, “At this singularity, space and time came into existence; literally nothing existed before the singularity, so, if the Universe originated at such a singularity, we would truly have a creation ex nihilo”.[2] While the public focusses on the incorrect idea of a bang or explosion in space, the vastly more profound and amazing aspect, that all space and time came into existence from nothing, is missed by the public, but clearly and consistently stated throughout peer-reviewed literature and statements by the scholars, “… the Universe’s beginning wasn’t an explosion. It was closer to an unfolding, or creation, of matter, energy, time, — space itself.”[3] A well-done documentary clip illustrates this phenomenal beginning.[4]

This is the reality of the origin of the Universe. What about alternate theories of an eternal universe without a beginning?[5] These possibilities were thoroughly explored, and at a conference in Cambridge, celebrating the 70^th birthday of Stephen Hawking, cosmologist Alexander Vilenkin discussed his paper summarizing current cosmology regarding the topic: “Does the Universe Have a Beginning?” He showed why the several theories put forward to escape our Universe having a beginning were invalidated, and further added, “All the evidence we have says that the Universe had a beginning.”[6] What a clear position: not the evidence for a beginning is better, more solid, or even overwhelms the evidence against, but all the evidence demonstrates the Universe had a beginning.

When all of the evidence supports a beginning, and there is no evidence supporting an uncaused, eternal universe, even an Ohio State University football player can figure out what that means. Please excuse my angst against the Buckeyes, I have been a Michigan Wolverine fan since childhood, and that excellent team to the southeast of us has caused me much grief over the past few decades.

Here is one interesting way to know the universe had a beginning: if any stars are still shining, the universe had a beginning. The stars of the universe run on fuel (hydrogen mostly, eventually burning heavier elements). Every second through nuclear fusion, the Sun turns around 600 million tons of hydrogen into 594 million tons of helium, and releases most of the remaining six million tons of matter as energy radiation and light. If every star we know of runs on hydrogen (and later in the star’s lifetime, some heavier elements too), then what would happen to the hydrogen supply, if the universe did not have a beginning, and was burning hydrogen forever? Clearly the universe would have RAN OUT OF GAS. This car gets one fill-up, and when it runs out, the lights go off. Our Universe came into existence with a certain amount of power, or ability to do work through time, and the law of entropy[7] indicates this ability to do work runs down over time, eventually leading to a cold, dark, dead universe, with nothing happening other than possibly a continued stretching of space.

[1] Not every galaxy is moving away from us. The exception is if a galaxy is close enough to allow the gravity between our galaxies to take over, then we will be on a collision course with that galaxy. We may have a collision course with the Andromeda Galaxy, but no worries, you will be long dead before that could occur.

[2] J. Barrow and F. Tipler, The Anthropic Cosmological Principle (Oxford, 1986), 442.

[3] Luz Kruesi, “Cosmology: 5 Things you need to Know,” in Astronomy (May 2007): 31.

[4] https://vimeo.com/145795089

[5] The 2003 paper by Arvind Borde and Alexander Vilenkin in co-operation with Alan Guth, the father of inflationary cosmology, extended the relentless grip of space-time theorems by proving classical space-time, in any possible universe or multiverse under the single condition of expanding on average, cannot be extended to past infinity (cannot be eternal without a beginning), but has to have a boundary (a beginning) at some time in the finite past.

We can then note either there is or is not something on the other side of, or beyond, that boundary. If not, then the boundary is the beginning of the universe. If there was something beyond the boundary, then that region or something will be described by a quantum gravity theory, or another theory not yet found. And if this is true, Vilenkin simply noted then that something will be the boundary or beginning of the universe. Either way, there is no escaping the universe had a beginning.

[6] Lisa Grossman, “Why physicists can’t avoid a creation event,” New Scientist 11 January 2012.

[7] Nature ceaselessly changes. The availability of energy to do work, as well as the amount of order in the universe inevitably decrease over time. Entropy is part of the second law of thermodynamics, which states the entropy of an isolated system, which is the measure of the decrease of available energy to do work and decrease in order, cannot decrease in time, but will continuously move toward the eventual maximum entropy, when energy loss is complete, and no further order can arise.

You can see this in your daily life: if you walk into an isolated room, carrying a boiling cup of tea, then scream, because you spilled some on your hand, and drop the expensive teacup to the floor, shattering it. If we consider the room an isolated or closed system, so no energy or ordering input can come from the outside, then:

1. The potential energy of the teacup being held by you was used up when the cup fell and broke apart.
2. The thermal energy of the heated tea molecules, measured by their moving much faster than the other molecules in the room, would disperse the thermal energy to the air and floor molecules, and eventually all the molecules in the room would reach the same temperature; equilibrium.
3. The sound waves of your yell of pain interact with the air and materials of the room, and eventually, like a pond that had a stone dropped in, would also reach equilibrium and go flat; no sound.
4. Without your tea, not to mention food or flow of re-oxygenated air, you would die, and over time your body, as well as other items in the room would not become more ordered, but instead would decay, once again reaching a point where energy loss and decay into disorder is complete.

Our universe, or larger multiverse if it exists, is in the same situation as the closed room. All types of energy and order disperse, having less and less available over time, until eventually reaching a point where the universe has no available energy to do work, just cold, dark, dead. This increase in entropy is known and studied in the diverse fields of chemistry, physics, cosmology, climate studies, information theory, economics, sociology, etc.

If the isolated room had existed forever in the past, then the boiling tea and colder room would have reached equilibrium and be at the same temperature an infinite time ago. Since our universe still has mountain tops strapped in ice, and stars still shining, then clearly the universe has not existed forever or we would have reached equilibrium temperatures an infinite time ago.

Whatever caused the universe has the ability to produce more usable energy, and order and information content, than the sum of all the energy, order and information ever available in the entire universe, or multiverse. That is an interesting fact to consider.