The farthest things we can see in the universe depend on how we look: with the naked eye, it's the Andromeda Galaxy (2.5 million light-years away); with powerful telescopes, we see ancient galaxies like GN-z11 (billions of light-years distant, seen as it was shortly after the Big Bang); but the absolute farthest "thing" is the Cosmic Microwave Background (CMB), the afterglow of the Big Bang itself, originating from the edge of the observable universe, about 46.5 billion light-years away in comoving distance.
About 95% of the universe is "invisible" because it's composed of dark matter (around 27%) and dark energy (around 68%), which don't emit, absorb, or reflect light, unlike the normal matter (stars, planets, us) that makes up the visible 5%. Dark matter's presence is inferred through its gravitational pull on visible galaxies, while dark energy is a mysterious force causing the universe's accelerated expansion.
The farthest object in space that you can see with only your eyes in the night sky is the Andromeda Galaxy. It is a huge spiral galaxy, and it is the closest large galaxy to us outside of the Milky Way. However, it is so far away that is only appears as a faint cloud in the night sky.
A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly 9460730472580.8 km, which is approximately 9.46 trillion km or 5.88 trillion mi.
Here's what that means. Voyager 1, NASA's deep-space probe, could soon become the first spacecraft to reach a historic milestone. In November 2026, the probe will be one light-day from Earth.
The special theory of relativity implies that only particles with zero rest mass (i.e., photons) may travel at the speed of light, and that nothing may travel faster.
Key Takeaways. The range of human vision is infinite. However, there are many factors that affect the ability of the human eye to see identifiable objects. The human eye can usually see up to three miles away on a clear day.
At a distance of 170.02 AU (25.4 billion km; 15.8 billion mi) as of November 2025, it is the most distant human-made object from Earth.
What lies beyond the universe? We are not sure but can theorize what lies beyond the universe that we know. Outside the bounds of our universe may lie a "super" universe. Space outside space that extends infinitely into what our little bubble of a universe may expand into forever.
In 1 sextillion years (10²¹ years), the universe will be a vastly different, dark place: the era of star formation will have ended, all stars will have burned out into white dwarfs, neutron stars, or black holes, planets will be cold and lifeless, and even protons might begin to decay, leading towards the "Big Freeze" or heat death, with only black holes slowly evaporating via Hawking radiation over unimaginable timescales. All familiar structures, including galaxies, will have long dissolved as the universe expands, leaving behind a cold, dark, and nearly empty expanse.
We are extremely confident black holes exist due to overwhelming evidence like stars orbiting invisible, super-massive objects (Sagittarius A*), gravitational waves from merging black holes detected by LIGO, and direct imaging of their shadows by the Event Horizon Telescope (EHT). While "100% sure" is rare in science, the consistency between Einstein's relativity, observed phenomena, and these new direct proofs leaves virtually no doubt within the scientific community.
While rarely encountered on Earth, it is estimated that 99.9% of all ordinary matter in the universe is plasma. Stars are almost pure balls of plasma, and plasma dominates the rarefied intracluster medium and intergalactic medium.
We know that light takes time to travel, so that if we observe an object that is 13 billion light years away, then that light has been traveling towards us for 13 billion years. Essentially, we are seeing that object as it appeared 13 billion years ago.
Both Voyagers will eventually collide with something, most likely the remnants of a star, but this will take an extraordinarily long time. The Voyagers' highest chances of collision were in the solar system, around the planets and in the asteroid and Kuiper belts, which they have already safely traversed.
For all we know, galaxies like the Andromeda Galaxy could be teeming with habitable worlds, some of which may even host intelligent life. But until definitively detected, for now the question as to whether life exists in the Andromeda Galaxy remains unanswered.
1 hour on Earth can equal 7 years in space (or vice versa) due to time dilation, a concept from Einstein's relativity where strong gravity or extreme speeds slow down time relative to an outside observer, famously depicted in the movie Interstellar on a planet near a black hole where an hour for the crew meant years passing on Earth. It's not about speed alone in orbit (ISS astronauts age slightly slower), but about proximity to immense mass, like a black hole, bending spacetime so drastically that time crawls for those nearby compared to time far away.
Return to the Moon
Artemis II, scheduled for launch between February and April sees the return of the first people to the Moon since Apollo 17 in 1972. Three American and one Canadian astronaut will orbit the Moon on a 10 day journey that lays the foundation for lunar landings in the coming years.
Where are Voyager 1 and Voyager 2 Now? Both Voyager 1 and Voyager 2 have reached interstellar space and each continue their unique journey deeper into the cosmos.
Instead of seeing the latest image in real time, humans actually see earlier versions because our brain's refresh time is about 15 seconds. So this illusion demonstrates that visual smoothing over time can help stabilize perception.
The human eye's theoretical resolution is often compared to 32K (around 32,000 x 18,000 pixels) for a full field of view, but its effective sharp vision is much lower, closer to 5-15 megapixels, as focus is limited to a small central area (fovea), with blurry peripheral vision. While the brain stitches these sharp points together for a detailed scene, we can't perceive a single 32K image all at once; recent research suggests the true limit of resolution is even lower than 8K for screens at typical viewing distances, meaning displays beyond 8K often offer diminishing returns for the naked eye.
On a clear day, you can see for up to 3 miles before the horizon due to the curvature of the earth. Yet you can see skyscrapers in a further distance than 3 miles due to no horizon obstruction. If you look into the sky you can see stars during the night that are millions of miles away.
The simple answer here, of course, is yes: space is silent because it's a vacuum. After all, what our ears perceive as 'sound' is just a pressure wave that passes through a medium, be that medium a solid, liquid or gas, and agitates the molecules within it.
1% the speed of light is 7 million miles per hour or 1,609,344 kilometers. That is unimaginably fast. To even do that is well beyond any technology we have or will have in our lifetimes.
Because astronauts like the ones on the International Space Station (ISS) are moving so quickly, they're also aging a bit more slowly than the rest of us. Due to a principle of physics known as time dilation, after a six-month stint on the ISS, returning astronauts are just a tiny bit younger than the rest of us.