What’s on the Black Holes poster
The rule, 3 worked examples, and the mistake everyone makes.
- The event horizon lies where the escape velocity reaches the speed of light.
- r_s = 2GM/c²
- The Sun = About 3 km
- Earth = About 9 mm
- Sagittarius A* = About 12 million km
- Common mistake: Picturing the horizon as a solid surface → It is a one-way boundary
Tidal forces, not the horizon, are what destroy an infalling object — and they are gentler for larger black holes.
Questions about the Black Holes poster
- What’s on the Black Holes poster?
- The rule, 3 worked examples, and the mistake everyone makes. The event horizon lies where the escape velocity reaches the speed of light.; r_s = 2GM/c²; The Sun = About 3 km; Earth = About 9 mm; Sagittarius A* = About 12 million km; Common mistake: Picturing the horizon as a solid surface → It is a one-way boundary. Tidal forces, not the horizon, are what destroy an infalling object — and they are gentler for larger black holes.
- Who is the Black Holes poster for?
- Black Holes belongs to the Physics section rather than to a school year, because physical science is not something one grade owns. Anyone learning relativity can pin it up — a beginner, a student mid-course, or someone revising years later.
- When should you use the Black Holes poster?
- The horizon is a boundary in spacetime, not a surface. Nothing special happens locally at it. A wall chart earns its place by being glanceable from where the work is happening, so Black Holes belongs on the wall where that physical science work actually happens, within glancing distance, rather than filed away.
- What other posters go with Black Holes?
- Cosmology, General Relativity and Gravitational Time Dilation sit alongside Black Holes in the Physics section. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.CosmologyGeneral RelativityGravitational Time Dilation
- Is the Black Holes poster free to download and print?
- Yes. Black Holes downloads as a free PDF with no account, no email and no watermark, like everything else in the Physics section. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
- What size does the Black Holes poster print at?
- Black Holes is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of Black Holes loses nothing.Printing guide
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