If just .001% of 10 billion Earth-like planets orbiting sun-like stars in the Milky Way have harbored advanced, intelligent life, shouldn’t we have seen some kind of evidence of their past existence, since this would equal 100,000 civilizations?

Great question! Complicated answer. Let’s start by looking Earthward at ourselves, then we’ll compare that looking spaceward toward the stars.

As you know, homosapiens are the advanced, intelligent life form on Earth which is now technologically advanced and space faring.

Now by some estimates, humans have been on this planet only for the last 200,000 years, or one fifth of one million years. There are a thousand million years in a billion years, and the Earth is about 4.54 billion years old. So, humans have been on Earth for only a tiny fraction of Earth’s existence. Here’s a graphic to illustrate that point and more to follow below.

This image illustrates what it would look like on a 24 hour clock comparing the age of Earth to the presence of humans. In fact, life itself has existed on Earth for less of half the lifespan of the planet, what to speak of humans.

So you can see, even though we have a planet in the goldilocks orbital region around our sun, someone looking at Earth many light years away would not see humans even though humans are here, because the light or radio waves haven’t reached them. They would assume this a dead planet. Humans have existed on this planet, in terms of a 24 hour clock, 1 minute and 17 seconds. In terms of exploring space, for less than 1 second.

You see, just because humans have been on Earth about 200,000 years doesn’t mean humans have been emitting radio waves and exploring space for all that time. In fact, we only began exploring space 60 years ago and emitting radio waves for a couple of hundred years. In the history of Earth, we have explored space (in terms of a 24 hour clock) for only a flash of a portion of a second.

That’s us. Now let’s look at the stars.

Let’s say there are 100,000 planets with advanced life like humans on them right now.

However, since the galaxy is 200,000 light years across, someone on a planet on the other side of the galaxy from us would not be visible to us. We’d see that as a planet with no human-like people because it would take light and radio waves 200,000 years to reach us. Now take into consideration that of the 100,000 planets with human-like people on them (as you suggest in your question), it took us 200,000 years to get to the point of emitting radio waves and exploring space. Hence, we’re looking for a very narrow window in a planet’s lifespan that intelligent life might be detected. Not only a tiny fraction of the planet’s existence has it had intelligent life, but only a tiny fraction of the time the intelligent life existed there were they able to emit radio waves and explore space, even if all conditions were favorable for that planet to eventually develop intelligent life.

Furthermore, the sky is very big. Looking for exoplanets, we have explored less than 3% of the total sky so far.

Put all of that together and the chance we would have detected other intelligent life is almost nil to date, even though it might still be out there somewhere. The guy below might be the exception.

Weird Things Happening

Some weird stuff is going on. Dark stuff.

We can look out and calculate that galaxies are spinning too fast and should fly apart but they don’t. So we think there’s too much gravity.

And so we came up with the notion there’s some invisible undetectable stuff called dark matter making up more than 96% of the universe.

Also weird is this lensing effect astronomers see, caused, they suppose, by said dark matter.

Yet we haven’t seen it directly nor detected it even though it should be all around us.

As I said. Pretty weird stuff going on. Leaves plenty of mystery in science.

What are the chances of two planets from the same solar system having sentient species that reach space exploration around the same time?

This is a great question, but unfortunately no one will be able to give a definitive answer as to the chances.

This is simply because we do not yet know if life exists anywhere other than Earth. It is still within the realm of possibility that Earth is the only place where any kind of life, what to speak sentient life, exists.

Finding such life would be an affront to many religions that contend that God created life on Earth only, and therefore finding even a fossil of a microbe on another celestial body would be the holy grail of science and have reverberating effects throughout human society. The theory of evolution would be proven.

It is believed to be highly likely that life does exist elsewhere in the universe simply by the laws of probability, but that being said, we have found no evidence to support this theory.

So now we can come back to your original question: “What are the chances of two planets from the same solar system having sentient species that reach space exploration around the same time?” Based on the fact that life has not been discovered anywhere, the chances to sentient life forms existing in the same solar system is practically nil (but not impossible).

Why doesn't anyone else besides me believe in time traveling?

I don’t know the answer to your question. However, consider this. We are not standing still. In time the Earth rotates around it’s axis, the Earth also rotates around the sun, the sun rotates around the galactic center and the galaxy is merging with Andromeda.
We are therefore moving at hundreds of thousands of miles per hour in space. Fast forward 10 seconds and you will find yourself in outer-space without a spacesuit!

Hypothetically, equally intellectual organisms are living on a near planet when and how would humans discover?

Hypothetically, we are living in an infinite universe. How far is a “near planet?”
If the planet is within a very close 200–300 light years, then there might be some possibility, within 200–300 years, that we might detect each other. If the life form is on the other side of the Milky-way, or in another galaxy, then there is no possibility.

sky space dark galaxy
Photo by Pixabay on Pexels.com

Would a possible alien lifeforms perceive time differently relative to ours?

I perceive time differently from other lifeforms. For example, when I was 7 years old I thought it would take forever to reach 10 years old. Nowadays, at 65, the years go by like months or days. If I’m busy, having fun, the day goes by faster by my estimation, and if my day is miserable it seems the day lasts forever. Sometimes I wish it could be the other way around!

Some lifeforms on Earth last only a few minutes and perceive time, if they perceive time at all, as a whole lifetime. My pets live 10–20 years, but that’s their entire lifespan. I, however, have had quite a few dogs, cats, even a parrot in my lifetime.

I imagine the same is true for critters on other planets.

What is combined single directional speed of earth rotation, Earth orbit, solar system transit, galactic spin and transit, and universal expansion?

Yes, we’re all over the place. Speed is relative. The sun orbits the galactic center at about 514,000 mph (143 mi/s) within its trajectory around the galactic center, but as we orbit the sun sometimes the Earth speeds up or slows down relative to the galactic center. Round and round we go. It’s kind of like this amusement park ride!

Is Earth mentioned in the Star Wars universe?

Everybody wants to jump on this bandwagon and throw in their two cents. Remember: Star Wars took place A long, long time ago in a galaxy far, far away.
Star Wars happened way in the past, not the future, perhaps even before the existence of Earth. Furthermore, it happened in a very distant galaxy, perhaps millions or billions of light years away.
It’s simply a modern miracle that we can watch the story unfold before us on the big screen and your Blu-Ray player! Earth is not mentioned, and if it were, the people of Earth during those days would have been primitive indeed, if even we had evolved into homo-sapiens at that point in time.

What would happen if NASA had the U.S. Military's budget?

We spend 600 billion dollars every year on the military. What would happen if NASA had that kind of money? Here’s a very cool YouTube video that I love to watch!
[youtube https://www.youtube.com/watch?v=chLOgj8xjx8&w=854&h=480]