eli5: If space is expanding faster than light in all direction. Why hasn’t the space between our atoms expanded to infinite?
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The extra space isn’t between atoms it’s between galaxies. Also, an “infinite” distance is impossible.
Space isn’t expanding faster than the speed of light. According to google, it’s currently expanding at ~40 miles/second.
Our current best model is that space *briefly* expanded *extremely* fast, in an event known as inflation. This inflation began and ended in roughly 10^-33 seconds, an unbelievably short blip of time. No, I can’t tell you how we calculated that.
One possible distant future for the universe is called *the big rip*, where expansion keeps accelerating, and yes – if space keeps expanding faster, eventually it’ll happen faster than gravity holds galaxies and solar systems together, and eventually faster than the bonds holding molecules together. If this is truez it would happen on the scale of 100 billion to 1 trillion years in the future.
Gravity, where it’s strong enough, does counteract cosmic expansion.
So there’s no expansion within galaxies, or within sufficiently massive galaxy clusters.
Not yet. Or at least possibly not yet. There are a few possible scenarios, and one of the them is the Big Rip, where expansion keeps accelerating until it does so exponentially, in which case there would cone a breaking point where in a short amount of time, galaxies, star systems, planets, molecules and finally atoms themselves are literally ripped apart.
The expasion rate of the universe is today estimated dto be around 73km/s /MegaParsec
The speed of light is around 300 000 km/s so two points needs to be 4100 MegaParsec apart of the distance in between to example at the speed of light.
1 parsec= 3.26 light years. 1 megaparsec = 3.26 million light years.
So 4100 MegaParsec = 13.3 billion lightyears
The atoms you talk about are not billions of lightyears apart, that is the distance required for space in between to expand at the speed of light. Atoms in molecules are less than a nanometer apart.
Let do come caulatioin and round to multiple of 10 for simplisity
13.3 billion lightyears = 12.6* 10^23 meter~10^24 meter, 1 nanometer = 10^-9 meter. This means the distance need to be 10^24/10^-9 = 10^33 times longer for the expansion to be the speed of light. That is another way to write 1 million billion billion billion times longer.
The speed of light is 3 * 10^8 m/s so the distance between to atoms expan by 3 * 10^8 /10^33 = 3* 10^-25 m/s
One year is 3600* 24* 365 =31536000s ~ 3*10^7 second
The mean a expansion at 3* 10^-25 m/s in a year is 3* 10^-25 *3*10^7 ~10^-19 m
The diameter r of a atom is around 10^-10 meters so the expansion is around 10^-9 of an atom.
So the space between to atoms expands by around 1 billionth of the diameter of a atome each year. That is counted by the forest that holds atoms together in molecules.
To get distance numbers that are a bit simple to understand, the expansion of space between Earth and the sun in a year is around 11 m. The distance to the sound is around 150 million kilometers = 150 billion meters It will not change the orbit because gravity counteracts it.
The rate at which the universe is expanding has yet to become stronger than the forces that keep everything together, the strong and weak nuclear force, electromagnetic force and gravity. If the speed of expansion ever gets stronger than any one of these it would lead to a “Big Rip” event signaling the end of the universe
Here is a video explaining it in greater detail
Space gets a bit larger, components of atoms get a tiiiiny bit further apart. But then they go back to where they’re supposed to be.
Repeat this tiny step many times, space is bigger, atoms are not. Grossly simplified.
Others have answered it well, gravity on the “local scale” of our bodies up to our galaxies is for now stronger than the expansion. But it seems the expansion is accelerating so eventually that big rip may occur.
You may have already seen it but if you are interested in the wider space side of this discussion, Kurzgesagt has a video on it. https://youtu.be/uzkD5SeuwzM?si=AeKx5JTlz5UN90R9
Space is NOT expanding. That is said as a shortcut way of explaining things in conversations.
A more accurate and true to theory way of explaining is to say there is ever more and more space.
It’s not expanding faster than light in **all** directions.
The shorter the distance the smaller the expansion rate. This also means, that the larger the distance the larger the expansion rate.
Things, within the local group of galaxies, are not moving away from each other, at least not because of the expansion, since the rate of expansion is smaller that the speed at which things are moving, and gravity is still the dominant player here.
Further away at larger distances we sometimes see galaxies moving towards us, but never overcomming the rate of expansion. So no matter how long they move towards us, they will never get here.
Even further away than that, at the largest distances, we see the rate of expansion exceeding the speed of light.
How many rips have occurred? Is all the dark matter and energy the remnants of previous rips? All the mass and energy is there we just can’t see it cuz it’s just random building blocks atm?
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