As the title says, if there’s infinite stars, wouldn’t the light from all of them have reached us and made our night sky become completely white from the number of stars there are? Is there just not enough stars in proximity to earth for all the light to reach us in time to see?
I’m sure there’s a simple answer, but it’s 1am here and my brain can’t figure it out.
In: Other
The Universe hasn’t been around forever, and therefore we can only observe stars and galaxies that are a specific and finite distance away. Therefore, we can only receive a finite amount of light, heat, and energy from them, and there cannot be an arbitrarily large amount of light in our night sky.
How has nobody mentioned Light Pollution? That’s why you see next to nothing in cities. The bright lights from all the streetlights and stuff essentially outshine the stars, their light has been traveling millions of years and isn’t nearly as bright
This is quite a famous question in cosmology. It’s known as [Olber’s Paradox](https://en.wikipedia.org/wiki/Olbers%27_paradox) and is posed in a very similar way to yours.
Funnily enough, the seemingly accepted explanation of this does not talk about stars, but about the remnants of the Big Bang. The idea is that the radiation that filled the universe at the time it first became transparent (if I recall correctly) about 300 million years after the bang) has been red-shifted by the expansion of the universe so it is now not visible light – this is the famous 3K background microwave radiation. This is an interesting take, but I’m not sure how it answers the paradox.
My original understanding (which may be bogus) is that even though the universe could be infinite, the observable universe – the parts from which light could reach us – is not infinite, and does not contain an infinite number of stars. Therefore, the basic premise (“every direction in which we look, we should see a star”) fails. I think this is sufficient.
It all has to do with the speed limit of the speed of light. Light is made up of small particles called photons. These only travel 1 light year (6 trillion miles/9.7 trillion kilometers) in 1 year. Stars that are 4 light years away take 4 years for the light to reach us. Stars that are 4 billion light years take 4 billion years to reach us. So not all of the stars there are have light that has reached us.
It also has to do with perspective. If you’re trying to see a dozen people and want to see all the people you would spread them out. But what about a million people? You wouldn’t be able to spread them out enough to see all of them, some would be hidden behind other people. Just like stars. And all of this happens while the people are constantly moving and so is the observer too.
You’ve hit on something called Olber’s Paradox. Brilliant people have been asking this question for hundreds of years, so you’re in good company.
No one pretends to know the *right* answer, but it’s likely a combination of the following –
1)Space is full of heavy things like galaxies that *bend* light away from us, like a lens. That light never reaches Earth so that star is invisible to us.
2) Space if full of clouds of dust and gas that absorb the light, like a dark tinted window, so we don’t see things behind those clouds.
3) Space is expanding which causes light to stretch out, which changes it’s “color”. So light that was originally red in color gets stretched out as it travels to Earth and is now X-rays, or Gamma rays, so our eyes cannot see it. This is part of the reason why we have X-ray Telescopes, to see that light.
4) Space is expanding and stars are still being born so the light from distant stars just hasn’t had enough time to reach Earth yet.
We do not definitively know that there are infinite stars. We only know that there are many. So yes, there is only a certain number of them, who’s light is currently reaching earth. So of them are already dead, and we only receive their last rays of light, some others are already up, but their first beams havent reached us yet. But between them is vast void of nothingness. (That is currently challenged by the theories about dark matter, but that certainly does not emit visible light soo)
There are not an infinite amount of stars, which is why our sky is not completely white.
Because our sky is not completely whited out by stars, it proves that the universe is not infinitely old, but had a beginning.
Because there aren’t infinite stars in the universe. There are an estimated 10^21 stars in the universe. That’s a lot, but not infinite.
a ) There aren’t an infinite number of stars, to our best of knowledge.
b ) Even if there were light takes time to travel. There is a concept called the “observable universe”, which is a sphere centered around the earth with a rough diameter of 93 billion light-years. Any stars further away than that will not be visible to us, as their light hasn’t had time to reach us.
The further a star is, the dimmer it is. If all the stars were at the same distance and close enough for us to see, the night sky would probably be a mix of red and white with some blue in between
Latest Answers