Hello! While a meat thermometer is the most accurate way to check the internal temperature of beef, there are a few other methods you can use:

1. Touch Test: This is a simple method where you compare the firmness of the beef with the firmness of your palm. For example, raw meat feels like the fleshy part of your hand when you touch your thumb and little finger together. Medium feels like touching your thumb and middle finger, and well-done feels like your thumb and base of the thumb. However, this method requires some experience to get right.

2. Cut and Look Method: Make a small cut in the beef and check the color. For medium-rare, the center should be pink and slightly brown towards the exterior. For medium, it should be light pink, and for well-done, it should be brown throughout. This method is not as accurate and can potentially dry out your meat.

3. Cooking Time: You can estimate the doneness of the beef based on the cooking time. However, this method can be inaccurate as it doesn't account for variables like the size of the beef cut, its initial temperature, or the exact heat of your stove or oven.

Remember, the USDA recommends a minimum internal temperature of 145°F (63°C) for steaks and roasts, and 160°F (71°C) for ground beef to ensure food safety.

Creating a homemade thermometer can be quite challenging and may not provide the accuracy needed for cooking. However, you can create a basic thermometer using household items, but it's more of a science experiment and not suitable for measuring the temperature of meat.

Here's a simple way to create a basic thermometer:

Materials:

• Clear, plastic, or glass container
• Water
• Rubbing alcohol
• Food coloring
• Clear plastic straw
• Modeling clay

Steps:

1. Fill about a quarter of the container with equal parts of water and rubbing alcohol.
2. Add a few drops of food coloring.
3. Put the straw in the container but don't let it touch the bottom.
4. Use the modeling clay to seal the top of the container, making sure the straw is held upright and not touching the sides of the container.
5. As the liquid heats up, it will expand and rise up through the straw.

Again, this is a basic thermometer and not suitable for cooking purposes. It's more of a fun science experiment.

For cooking, it's best to use a proper meat thermometer to ensure the meat is cooked to the correct temperature for both taste and safety. If you don't have one, using the methods I mentioned earlier (touch test, cut and look, or cooking time) would be more suitable.

Yes, you could potentially use boiling water as a reference point since it boils at 100 degrees Celsius (212 degrees Fahrenheit) at sea level. However, this method has its limitations and may not be entirely accurate.

Here's a basic way you could try to calibrate a homemade thermometer:

1. Heat a pot of water until it reaches a rolling boil.
2. Insert your homemade thermometer into the boiling water and mark the level the liquid in the thermometer rises to as 100 degrees Celsius or 212 degrees Fahrenheit.

However, there are a few important things to note:

• The boiling point of water changes with altitude. If you're at a high altitude, water boils at a lower temperature.
• This method assumes that the behavior of the liquid in your homemade thermometer is linear, which might not be the case.
• This method won't give you a precise measurement of 90 degrees. It's just a rough estimate.

For cooking, especially for meat, precision is important for both safety and quality. Therefore, I would still recommend using a proper meat thermometer if possible.