Just walk away. There is no convincing someone who is that far away from reality. You’ll waste your time and energy better spent elsewhere.

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This is not true.

I worked (in the early 90s) on satellites for EUMETSAT, writing and testing code for the latest Meteosat constellation of remote observation craft.

The imagers did not use a 'fish eyed lense'.

The Earth, like all planets, is essentially spherical as a quick trip to the seashore can demonstrate.

How? Have you ever free dived? How far can you make it before the pressure breaks an ear drum?

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I am genuinely curious why you feel this way.

The truth about the universe is more incredible, more complex, and more fantastical than the best written fiction. Certainly better than the garbage they shovel on tiktok.

From quantum entanglement to the warping of spacetime. From the forging of the heavier elements in the heart of ancient dying stars to the evolutionary magic that took those elements and made you and I. From how water uses the polarity of its bonds to dissolve things to how our bodies use ATP to fuel our existence. Reality is wonderous.

I will take science over any fantasy any day of the week.

You said two things. Earth is hallow and we live inside the hallow area. So if we lived in a cave what is space? Literally you can look up and see we are not in a cave we’re floating around something. Second we’ve dug as deeply as can be reached and there’s always more dirt/stone. We’ve take what would be equivalent to an X-ray of the earth. By sending radio waves through the earth to different points we can measure the thickness of the earth. This is how they estimate time for a volcano to erupt by detecting when magma chambers are filling. You can also measure the volume of earth and compare it’s motion and gravitational effects to see if they equal out. Lots of ways to prove it

Or OP's apparently. He's just as brainless.

It's hard to give a proper counter point to something as stupid as "the earth is hollow because of fish eye lenses". The fact that you can see space and stars obviously debunks the claim. I'm now very curious how this convo went down. Assuming this isn't trolling because it sure feels like it.

You are the worst kind of idiot. How do you breathe?

You could tell him to check out the Kola Well. They drilled 40,000 ft into the earth.

"Much information comes from such holes; for example, the bottom of this hole was about 370°F (190°C).

The structure of the deep Earth is studied today by means that are more indirect. Perhaps the most effective method has been from studying earthquake or seismic waves as they move from one sensing station to another. These natural waves allow us to see inside the Earth as they react to various layers, much as x-rays or MRI’s allow us to view inside the human body." https://www.uu.edu/dept/physics/scienceguys/2003Apr.cfm#:~:text=The%20deepest%20hole%20by%20far,7km%20(about%2023%2C000ft).

So we know for a fact the earth isn't hollow.

I think I have this figured out.

There is no friend, homie here is like 14 and is embarrassed to ask on behalf of himself, so is telling this story.

Would be interested to hear how hollow earth nonsense accommodates the motion of the sun, the stars, and the planets; how it explains observable redshift of galaxies millions or billions of light years away from us (even an amateur can measure this); why a shadow is shorter or longer depending on longitude in a way that correlates with us living on the outside (not the inside) of what is essentially (although not exactly) a sphere; or how one can easily measure the curvature of the sphere using a laser and detector a mile or two apart.

None of these have anything to do with fisheye lenses.

This is just scratching the surface. There are tons of real world phenomena that just don’t work with a hollow earth.

Exactly. Cui bono. Who benefits from this?

Wide angle lenses are used on many Low Earth Orbit spacecraft, rovers on Mars, etc. in order to fit more visual information into the frame.

If that's a major sticking point for them then you can show images from the Apollo missions, etc. You can even look up what cameras and lenses were used. If they don't think we went to the Moon, show them images from the Lunar Reconnaissance Orbiter of the Apollo landing sites and rover tracks.

But in all probability, your buddy doesn't really care about space, the shape of the planet, history, science, camera specifics, or anything to do with understanding nature for it's own sake. They probably just want to FEEL superior through special or hidden knowledge. As far as I know there's no remedy for that besides some form of ego death.

Fisheye lenses produce a distortion that makes straight lines appear to curve away from the center. Your friend's argument is perhaps that pictures of a curved horizon are just demonstrating this artifact. Indeed, many hobbyist rockets flown with a GoPro on board show this behavior while not reaching enough altitude for curvature to be reasonably visible.

When horizon curvature is due to a lens effect, then when the camera pans such that the horizon crosses the center of the image, we expect the horizon's curvature to switch as well. But there are plenty of photos and videos taken from enough altitude that demonstrate that this doesn't occur. So at least these are not showing curvature just due to use of a fisheye lens.

Now perhaps those cameras were purpose-made so that they bend everything the same direction. Or maybe the pictures are photoshopped! Or maybe you're just looking at the screen wrong! You can come up with an infinite number of reasons not to believe in picture evidence. In fact, you can come up with an infinite number of reasons not to believe any evidence at all. It's just that when you go to do any activity that actually requires taking into account the curvature of the earth, you will be wrong.

Many of these activities are hard to do, for instance: building a GPS receiver, navigating a ship across an ocean, or sending a spacecraft to the moon. But there are easier things that immediately require spherical trigonometry, such as: predicting time of sunrise and sunset for any position on earth and any time of year, or predicting which stars will be visible in the sky, or where the moon will be. To carry out these calculations and still believe the earth is anything but near-spherical requires willful misimagination.

Perhaps a better question is: suppose the images were taken with a fisheye lens. So the horizon is actually straight and not curved. But if the earth were hollow why would there be a horizon at all? In images from space, when you look at the horizon, you see the ground stop, then the sky begin, then space begin. You wouldn't see black there if the earth were hollow. So this fisheye lens claim actually rules that out. If your friend really believes all these photos are real but were taken through a fisheye lens, perhaps he should at least be arguing that the earth is flat.

I wrote all that out in case you really wanted to read a response to this fisheye lens claim. Most likely none of that will be useful for your friend. All the other commenters here are basically right: it's less likely that your friend is wrong out of ignorance (correctable with more information) than that he is pranking you or will never stop being wrong.

The thing I like most about this stuff is how it humbles me, sure I like space and science like most people but I can not understand all the math or interested in how the sausage is made, just tell me some cool shit and show me some pictures.

If people are accredited I will trust them more, if it is some youtube guy I will trust him less.

I love understanding but am also not so proud that I pretend to understand something that I can not back up.

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Unless he has seen the cameras himself with his own eyes and knows how to identify fish eye lense or not, then hes just taking the word of someone who says its fisheye th same way he accuses others of taking peoples word its NOT fisheye.

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There was a group of followers in the early 1800's who did believe we were living inside what is called a Dyson sphere (I'm gathering that's what your friend is describing right?) If that's the case then what about the planets we can actually see? They'd have to be contained within this sphere as well if that was the case, and the un8verse itself would be within this sphere that is earth.

We know that's just not true.

How would we be able to predict observable things like solar eclipses years, decades, or even centuries in advance if our model of the solar system was not accurate?

How does your "friend's" theory account for those things?

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You can't argue with logic against willful ignorance. That wasn't a scientific argument.

As for factual evidence, go outside and look up.

Edit: reading OPs other replies, I think they are the "friend" in this scenario and looking for ways to convince others we live in hollow earth.

He's fucking with you my dude