Search keywords
- why cosmology doesn't make sense
- what we don't know about black holes
- what do we know about black holes
- what do gravitational waves actually observe
- why we can't directly observe Earth's interior
- dark matter dark energy unsolved
- direct observation vs indirect observation vs theory
- go NASA
1. Why does cosmology, of all things, never quite click?
Everyday logic and everyday physics make decent sense to me.
Drop something and it falls. Push something and it moves. Touch something hot and it's hot. Go deeper underwater and the pressure goes up. At the center of the Earth, gravity pulls in every direction and cancels out, but the pressure is crushing from all sides.
In cases like these, intuition and theory line up pretty well.
But once the topic turns to space, it suddenly gets hard to buy.
Black holes. Gravitational waves. Warped spacetime. Dark matter. Dark energy. The expanding universe. Singularities.
By this point you start thinking, "Wait, do they really know that?"
I think that's a perfectly healthy way to doubt.
Cosmology isn't a finished product where everything is neatly understood.
Some parts are understood very well, and some parts are honestly still unknown, all mixed together.
So the point isn't to handle space science with a crude "believe it or not."
What we've observed directly. What we've strongly inferred from indirect evidence. What theory predicts should happen. What we still don't know.
The point is to keep these four apart.
If you skip that and say "we know it all," you end up doing some pretty sloppy, pseudo-science-style hand-waving.
2. The name "black hole" is confusing from the start
The name "black hole" is misleading.
It makes you picture an empty space cut out of something, like the hole in a donut or a nostril.
But NASA describes a black hole as not a hole in the true sense, but a huge amount of matter packed into a very small space. Inside the event horizon (the boundary of no return), gravity is so strong that even light can't escape.
So rather than "a hole in the universe," a black hole is closer to
a region where gravity is so strong that there's no route back out.
If you want a Dragon Ball comparison (a hugely popular Japanese manga and anime), the starting point "the planet of King Kai, where gravity is extremely strong" is actually pretty good.
But a black hole isn't just a souped-up version of King Kai's planet. It's a whole other level of bad news.
- King Kai's planet: gravity is heavy, but with effort you can move around and leave
- Black hole: once you cross the boundary, not even light can come back
- King Kai's planet: a training ground
- Black hole: a cosmic prison where the exit simply no longer exists
So a black hole is less a "hole" and more a state where, under the laws of physics, the way back is gone.
3. "Spaghettification" has never been observed on a human
People say that if you fall into a black hole, you get stretched out like spaghetti.
But here too, it's best not to act like we know more than we do.
Nobody has filmed a human falling into a black hole and stretching like a noodle.
Of course not. We haven't observed that.
The basis for spaghettification is mainly the theory of tidal forces, plus observations that can be interpreted as a star being torn apart as it nears a black hole.
A tidal force is the force that arises because gravity is stronger on the near side of an object than on the far side.
Say you fall in feet first. Your feet are closer to the black hole. So your feet get pulled harder. Your head gets pulled a little less.
That difference stretches you lengthwise. At the same time, you get squeezed from the sides.
That's the basic picture of spaghettification.
Still, it's worth sorting out what's what here.
- Objects getting stretched by differences in gravity: theoretically very solid
- Stars apparently being torn apart near black holes: observed
- Footage of an actual human being spaghettified: never directly observed
- What ultimately happens inside the event horizon: there are parts we still don't understand
NASA also says that what happens to matter after it crosses the event horizon is still not exactly understood.
Mixing these together and saying "we know everything" is a bit sloppy.
I think the most honest way to put it is this.
Near a black hole, tidal forces are predicted to stretch objects, and there are observations that can be interpreted as a star actually being torn apart. But nobody has directly observed a human-sized body being spaghettified, and the inside of a black hole still has unsolved parts.
That level of claim feels about right.
4. At the center of the Earth, gravity cancels out, but the pressure is enormous
When you think about gravity, a question naturally comes up.
On Earth, things are pulled toward the Earth's center. So what would happen if you were at the center?
The answer: in a roughly spherically symmetric model, gravitational acceleration at the Earth's center is nearly zero.
That's because there's Earth's material in every direction around you.
You're pulled to the right. You're pulled to the left. You're pulled from above and from below.
If it's perfectly symmetric, those pulls cancel out.
But the important point here is this:
Nearly zero gravity does not mean safe.
At the Earth's center, the pressure is brutal from every direction.
Even if the directions of gravity cancel, the pressure from the weight of all the material above you keeps building up.
So the Earth's center works out like this:
- Gravitational acceleration: close to zero at the center
- Pressure: among the highest anywhere
- Temperature: extremely high
- A human: dead instantly
You could call it "feels like zero gravity, but really it's hell, squeezed from every side by the weight of a whole planet."
5. We haven't looked at the Earth's interior directly either
This matters too.
Humanity has never gone to the center of the Earth and looked around.
Our knowledge of the interior is mostly inferred by combining seismic waves, gravity, the magnetic field, heat flow, rock experiments, and the Earth's motion.
The USGS (the U.S. Geological Survey) also explains that current information about the Earth's interior comes from the paths and characteristics of seismic waves, experiments on rocks and minerals under high temperature and pressure, and the Earth's gravity, magnetic field, and heat flow.
In other words, about the Earth's interior too, the situation is:
We haven't seen it directly. But multiple lines of indirect evidence agree with each other very strongly.
You can't say "if they haven't seen it directly, it's all a lie."
But claiming it as if we'd seen it directly is wrong too.
Here as well, direct observation, indirect observation, and theoretical inference need to be kept separate.
6. Gravitational waves let us see space, so why can't we CT-scan the Earth's interior?
If gravitational waves let us see the universe, couldn't we use them to see the gravity inside the Earth?
That's a very natural question.
But gravitational waves and the Earth's gravitational field are different kinds of things.
Gravitational waves are ripples in spacetime produced by violent events such as black hole mergers.
On September 14, 2015, LIGO (a U.S. gravitational-wave observatory) announced the first direct detection of gravitational waves, coming from the merger of two black holes.
That's a story of "spacetime shook far away in the universe, and the shaking reached Earth."
The gravity inside the Earth, on the other hand, is basically a static gravitational field.
It's not something that arrives as a wave.
Of course, the Earth's gravitational field is measured.
NASA/JPL's GRACE-FO is a mission that measures changes in the Earth's gravity field to track the movement of water and changes in mass at the surface.
But that doesn't let us CT-scan the Earth's interior cleanly.
With gravity alone, the information gets mixed together.
Suppose a satellite or a ground measurement shows "gravity is slightly stronger here." Is that a density difference in a shallow layer, a deep structure, groundwater, ice, or the mantle? It's hard to pin that down from gravity data alone.
So to look inside the Earth, you have to combine gravity with seismic waves, the magnetic field, rock experiments, numerical models, and more.
In other words:
Seeing space with gravitational waves → Detecting violent shaking of spacetime.
Looking at gravity inside the Earth → Measuring the unevenness of a quiet gravitational field created by how mass is distributed.
Fully imaging the Earth's interior → Not possible yet. The information gets mixed, and you need to combine it with seismic waves and other data.
7. Cosmology is a mix of "what's been confirmed" and "what we still don't know"
I suspect this is why cosmology is so hard to swallow.
Space science gets a lot right.
Gravitational waves have been detected. The shadow of a black hole has been photographed. General relativity has held up against a huge range of observations. The Earth's interior has been strongly inferred from seismic waves and other evidence.
On the other hand, what we don't know is also huge.
What is dark matter made of? What is dark energy? What happens inside a black hole? Does a singularity really exist physically? How do gravity and quantum mechanics fit together? How should we even treat the beginning of the universe itself?
ESA (the European Space Agency) explains that ordinary matter is only a small part of the universe, and that more than 95% of the universe's mass and energy is made up of dark matter and dark energy. And about dark matter, it says we still don't know what it's made of.
That's a big deal.
In other words, modern cosmology is in a state where
It's right a lot of the time. But it isn't the final answer. And humanity still doesn't know most of the universe.
So feeling that "I can't buy the explanation of space" isn't strange at all.
If anything, I think it's natural to feel uneasy when people act like they understand even the unsolved parts.
8. Look at science by sorting it, not by faith
Asking whether you "believe in science or not" is a bit crude.
What matters is sorting out which level of claim you're hearing.
| Level | What it means | Examples |
|---|---|---|
| Direct observation | Actually detected, photographed, or measured | Detection of gravitational waves, photographing the shadow around a black hole |
| Indirect observation | Strongly inferred from results | Earth's internal structure, behavior of matter around black holes |
| Theoretical prediction | Predicted by the equations | Spaghettification, cancellation of gravity at the center |
| Unsolved | Still not understood | Inside black holes, what dark matter is, quantum gravity |
Keeping this table in your head makes it much easier to listen to space talk.
"Did they see that directly?" "Is it indirect observation?" "Is it a theoretical prediction?" "Or is it still unknown?"
Just sort it like that.
You don't have to doubt everything. But you don't have to believe everything either.
What's known is known. What's unknown is unknown.
That's enough.
9. Conclusion: space doesn't click because humanity's explanation isn't finished, not because the world is glitching
The universe doesn't look like a device built with a purpose.
Black holes don't look like things placed somewhere for a reason, either. They look like what happens when the rules of gravity, mass, and spacetime get pushed to their limit.
So if you ask "what's the purpose of their existence?", you'll probably short-circuit your brain.
The universe is a world of explanations by conditions, not by purposes.
When conditions are met, stars form. When conditions are met, stars collapse. When conditions are met, a black hole forms. When conditions are met, gravitational waves are emitted. When conditions are met, we can observe them.
But the fundamental laws underneath those conditions aren't fully understood yet.
So I think this is the best attitude toward cosmology.
Admit what's known. Say "we don't know" about what isn't. Don't talk about things nobody has observed as if they had been. Don't turn theoretical predictions into a faith. But don't carelessly dismiss the parts where observation and calculation agree.
I think that's a pretty honest way to relate to the universe.
The universe: I don't get it.
But it's precisely because I don't get it that it's fun.
Go NASA ❤
References / Sources
- NASA Science, “Black Holes”
- NASA Science, “Black Hole Anatomy”
- NASA Science, “What Happens When Something Gets ‘Too Close’ to a Black Hole?”
- NASA JPL, “How Scientists Captured the First Image of a Black Hole”
- LIGO Caltech, “Gravitational Waves Detected 100 Years After Einstein’s Prediction”
- ESA, “The dark Universe”
- USGS, “The Interior of the Earth”
- NASA JPL, “GRACE-FO”
