We all know the universe is big. About 35 years ago we sent Voyager out into space and it is our fastest-traveling vehicle at over 35,000 mph. It only just recently made it out of our solar system. It will take Voyager another 40,000 years traveling at this speed to finally escape the sun’s gravity as the dominant force.
By that time, it would only be halfway to our nearest star, Proxima Centauri. We have over 100 billion stars, just in our galaxy.
If instead we were to spend that 40,000 years traveling at the speed of light, we could make it clear to just the other side of the center of our Milky Way galaxy.
But to make it, even at the speed of light, to our closest galaxy Andromeda, would take 2 million years. Voyager, even if it left doubly as old as the universe ago, would still not quite make it to Andromeda.
Our sun is large, and bright. We use a lot of energy here on our planet. In just one second the sun produces more energy than all of us on the Earth consume in a half-million years, at current consumption levels.
The sun is enormously compact — so much so that a photon of light emanating from the nuclear reaction takes over 100,000 years just to make it’s way to the sun’s surface to reach us.
The sun is made of hydrogen, compacted and crushed together into helium. Each second 700,000,000 tons of hydrogen are converted into 695,000,000 tons of helium and 5,000,000 tons of energy.
Our sun is average. In about 5 billion years it will run out of hydrogen then quickly burn the helium, puff out huge beautiful clouds, then slowly cool as a little white dwarf, not much bigger than the Earth.
All that we see in the sky are stars, or clouds lit by stars. It’s only been fairly recently (20th century) that Hubble, the man, not the telescope, discovered that not all the lights in the sky are just stars. Some are vast collections of stars — other galaxies.
The most abundant element in the universe is hydrogen, or so we have thought. All stars have burned this element. Even more recently we’ve found that perhaps hydrogen is not the most abundant matter. If we take all the stars and all the planets, moons, nebula – we find that far more matters is needed than what we can see to explain the motions and behaviors we detect. This unknown matter that no one has ever seen has been named Dark Matter.
Dark Matter exerts gravitational forces on all matter.
We’re all flying apart from each other, but have originated from a common source. All that we are able to see is matter.
However, if you take all that we can see in the universe, in all its hugeness, and multiply that five-fold again — you will find how much of the universe exists that we have not yet been able to see. It is Dark Matter. Even in our local Milky Way, over five times the mass of what we can see exists somehow, invisibly, yet exerting a gravitational force upon us.
This is why our galaxy, and other galaxies, do not fly apart as they spiral around. The gravity of Dark Matter binds them together. We have never detected Dark Matter, and have no idea what it is.
And if that were not strange enough, all our universe continues to explode out from the Big Bang, with all galaxies flying apart from one another. But this expansion is not slowing down like common sense tells us it should. This expansion is speeding up. We are flying apart from each other faster and faster.
Scientists have named the energy required to account for this, Dark Energy. It seems to have a negative gravitational force, pushing things away from each other. But really it behaves more like a flattening or leveling of the ripples of space-time. Dark Energy accounts for far more of the universe than anything else.
In fact, Dark Energy makes up 70% of the universe. We have no idea what it is. Dark Matter makes up 25% of the universe. We have no idea what it is. All that we have seen of our universe in all its vastness and complexity only makes up 5% of the universe.
Earlier today NASA announced some findings in conjunction win STSCI that came from the Hubble Space Telescope. Scientists have been able to determine that Dark Energy has been exerting its repulsive force clear back in time, even toward the Big Bang.
Einstein thought that eventually the universe would cease its expansion under the force of gravity, reigning itself back in to implode once again. He created the concept of the cosmological constant to counter some of the force of gravity pulling things back together. This cosmological constant with its slightly repulsive force would emanate evenly from all places within empty space. He didn’t much like it, but it was necessary, and it turns out he was right.
So today marks the day that one more bit of knowledge related to Dark Energy has come to light. We are now able to say that the substance with comprises 70% of the universe was around even toward the Big Bang. That may not sound like much, but but it’s really hard to learn about something that is completely invisible and undetectable directly.
And considering that we are only able to even detect and know about 5% of the entire universe, it’s a great little baby step: we now know that about 6 billion years ago, Dark Energy began to exert more repulsive force than the gravity of visible matter, and our invisible ally Dark Matter, could counter.
In fact, it’s really much more between Dark Energy and Dark Matter – our baryons that make up everything we know are pretty insignificant in this.
With Dark Energy winning, the universe should continue expanding away faster and faster, until the suns burn out and worlds grow cold, and all that is left is pure darkness and absolute zero. Then, eventually, even the very substance of matter dissolves.