A flame can produce a shadow if the other light source is much brighter, then refracted by the temperature difference, or the flame produces soot, steam, or other combustion products.
Flat-Earthers discovered images of flames not casting a shadow, & when they saw in a photo that a rocket’s exhaust casted a shadow, they used it as “evidence” it was faked. In reality, a flame can produce a shadow under the right conditions. Rockets have opaque combustion products, & in daylight, are lit by the very bright sun.
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The GoFast rocket is considered to be the first amateur rocket to reach space, beyond the Kármán line. The rocket was spin-stabilized through ascent. After reaching a certain altitude, it used the yo-yo de-spin mechanism to reduce the spin rate.
Flat-Earthers noticed the rocket’s spinning motion suddenly slowed, and they used it to “prove” the rocket “hit a barrier” up there. In reality, a yo-yo de-spin mechanism was deployed to slow the spin, but the rocket was still going up for some time afterward. — Hitting a barrier would have destroyed the rocket.
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The first image of Earth from space was taken by the V-2 No. 13 rocket in 1946 using the DeFry 35mm movie film camera and a 50mm lens attached to the rocket. The camera had a relatively narrow field of view. As a result, Earth’s curvature is only very slightly visible.
Flat-Earthers claim the flat appearance in the photo “proves” a flat Earth. In reality, 1. by careful examination, we can see the curve, 2. the camera has a narrow field of view, reducing the visible curvature, 3. the photo shown by flat-Earthers is usually a cropped version, further reducing the visible curve, and 4. the photo matches the expected curvature according to simulation.
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Rocket engines produce thrust by releasing mass rearward at a very high speed according to Newton’s third law, not unlike how discharging a fire extinguisher pushes us backward.
Flat-Earthers claim that rocket engines cannot possibly work in space because space if vacuum and there is no air to push against. In reality, it is possible to produce thrust in a vacuum by releasing mass —that we call “propellants”— rearward at a very high speed.
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Flat-Earthers like to dismiss any evidence of spherical Earth by mentioning that we never went to space to witness it ourselves. In reality, to go to space, we need to know Earth is a sphere in the first place and other related knowledge, like gravity.
We knew Earth is a sphere 23 centuries before the first spaceflight. And it is easy to verify Earth is a sphere from simple observations that anyone can do from Earth’s surface.
Flat-Earthers often challenge us to provide a video of a rocket launch that was taken from the rocket itself, without interruption from launch to reaching space, as if it would convince them to accept that it is real and the Earth is a sphere.
The launch video of the 2001 Mars Odyssey mission easily fulfills their demand. But whether they can manage to accept the reality that Earth is a sphere is entirely another matter.
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Rocket launches have a curved trajectory because their objective is not only to reach space but also to enter Earth orbit. To achieve it, a spacecraft needs to gain a sufficient horizontal speed, parallel to Earth’s surface.
Flat-Earthers claim the curved appearance of a rocket launch trajectory “proves” rockets never reach space. In reality, it is caused by the motion of the rocket parallel to Earth’s surface, perspective effect, and the curvature of the Earth.
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Rockets consist of several stages. Two or more smaller rockets are combined into a single rocket. They are ignited in order; when an earlier stage runs out of propellants, it is jettisoned to reduce the load for the rest of the rocket.
Flat-Earthers noticed videos of rockets being recovered from the ocean and use them as “evidence” rockets never went to space. In reality, these are the jettisoned earlier stages of the rockets. The latter stages do reach space.
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A satellite in a high enough orbit can remain operational for a very long time because in space there is practically no air resistance. This is a situation that never occurs in our everyday life. A car requires a constant consumption of fuel to keep running, but a satellite can remain in motion without consuming any fuel because there’s practically no force stopping it.
Flat-Earthers claim that satellites cannot stay up there for such a very long time because ‘we never refuel any satellites.’ They are wrong. In space, there is practically no drag, and satellites only need to consume fuel to adjust their speed periodically.
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Most combustion engines work with oxygen from Earth’s atmosphere as its oxidizing agent in the combustion process. But in the case of rockets, there’s no oxygen in space. It would have to bring the oxidizer in addition to its fuel or use monopropellant which doesn’t require an oxidizer.
Flat-Earthers claim rockets should not be able to work in space because there’s no oxygen in space. They are wrong. The lack of oxygen in space is merely an engineering problem which is not impossible to solve. Rockets are engineered to carry its oxidizer or utilize monopropellant which does not require an oxidizer.
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