You have probably heard somewhere that the universe is expanding. Hearing this can bring up all sorts of questions. How does this affect our solar system? Will we drift away from the sun? Why is the Universe expanding anyway?
You are in the right place if you have any of these questions. We can answer them all and help you gain a better understand of what this means for our home planet.
Why is the Universe expanding?
The universe was initially caused by the Big Bang. When we think about the Universe expanding we tend to jump immediately to this.
However the expansion of the universe is not about astronomical bodies and materials aggressively flying away from each other, a majority of things are static.
The stars, for instance, are standstill in relation to spacetime fabric, which is expanding. A great way to visualize this is to imagine a grid. Imagine two dots at different points.
If the whole grid gets larger and the squares get bigger then it will look as though the dots are growing apart. Which they are, but they are staying in the same place that they began in. In this sense, the grid is spacetime fabric and the dots are stars.
The Universe is continually expanding, and it is not expanding as you may think. It is not expanding from one point, if it was then you would be able to see a specific point from which all the stars and galaxies moving away.
What is happening is that space itself is expanding there is no logical center.
How does this expansion affect galaxies?
Every galaxy is made up of astronomical bodies, all orbiting other objects and each will have a set path they have been on a long time.
Each galaxy will start to distance from one another as they are expanding away due to this universal expansion. However, objects inside the same galaxy will not be affected in the same way that the galaxies are.
In short, this means that the distance between the earth and the sun will not be affected in the same way the distance between our galaxy and perhaps the andromeda galaxy would be.
It is similar to how the distance between atoms will also not be affected. There is no need to worry that the expansion of the Universe also means the expansion of you, that is not how it works.
This may make your brain tick, even more, probing the question, ‘What is stopping galaxies from expanding in the same way?’
The reason that a collective galaxy won’t expand as the universe does, is because of gravity. Gravity is binding in nature.
Think about our galaxy and our solar system too. We orbit the sun, and our solar system orbits a black hole, much like the rest of the Milky Way galaxy does. This happens due to the gravity of our sun and the black hole.
A powerful force with a great deal of mass has a high center of gravity, which tempts other objects to orbit it.
Thus, the expansion of the universe doesn’t affect galaxies simply because there are so many astronomical bodies in close proximity to one another than there are in outer space and beyond galaxies.
To put it simply, closer proximity means more gravity, more gravity means more immunity to universal expansion.
How do we know this is happening?
One of the most confusing things you will hear is, ‘ the main reason that we know the universe is expanding proves that our galaxy is not affected by it’.
If all of our measuring equipment was expanding at the same rate that the universe is, we would notice a difference.
Much like if your tape measure grew at the same rate that you did, you would always measure at the same size.
But because this is not the case, our measuring equipment stays the same and therefore we are able to notice the difference in our measurements of the Universe.
How does this affect our Earth and our Sun?
Long story short, it doesn’t.
That being said the earth is moving away from the sun, and the expansion of the universe will not affect our solar system, but gravity eventually will. Let’s explain.
First of all, the Universal expansion won’t affect our solar system in the way that it affects galaxies, as it pushes them outward. But due to the force of gravity being more powerful than the force of expansion, it will bring upon other effects.
In about 5 billion years the Andromeda galaxy will collide with ours, despite the expansion of the universe, this is due to gravity. As other galaxies draw away from us, Andromeda draws closer, but this is due to gravity and not due to the expanding universe.
Similarly, we are drifting from the sun, but again this is nothing to do with the Universe expanding. Each year the earth drifts away from the sun by about 0.6 inches. There are a few different theories as to the exact cause of this, a primary one simply being ‘gravity’.
Or in some sense, a tidal activity which is also something that is affecting the distance of our moon to us and how it affects our ocean tides. However, the distance between the earth and sun is down to gravity and other factors within our own solar system and not the universes’ expansion.
Our universe is expanding, pushing galaxies away from one another and increasing in size. This does not affect the astronomical bodies within these galaxies though due to the gravity produced by the closeness of these bodies.
This means that the expansion of the universe will not affect the distance between us and the sun.
That being said the distance between us and the sun is being affected by other factors, but the expansion of the universe is nothing to do with this phenomenon, that is a whole other thing.