French physicist Gaston Plante invented the lead-acid battery in 1859 – almost 50 years before Einstein developed his theories of relativity. Now scientists have found that the lead-acid battery, which is commonly used in cars, strongly relies on the effects of relativity. Specifically, the scientists calculated that 1.7-1.8 volts of the lead-acid battery’s 2.1 volts (or about 80-85%) arise from relativistic effects. “This is a new, well-documented case of ‘everyday relativity,’” Pyykkö told PhysOrg.com. As the scientists noted in their study, the finding essentially means that “cars start due to relativity.”
The lead-acid battery is the oldest type of rechargeable battery, with the main component being lead. With an atomic number of 82, lead is a heavy element. In general, relativistic effects emerge when fast electrons move near a heavy nucleus, such as that of lead. These relativistic effects include anything that depends on the speed of light (or from a mathematical perspective, anything that involves the Dirac or Schrödinger equations).
The lead-acid battery contains a positive electrode made of lead dioxide, a negative electrode made of metallic lead, and an electrolyte made of sulfuric acid. Through their calculations, the scientists found that the battery’s relativistic effects arise mainly from the lead dioxide in the positive electrode, and partly from the lead sulfate created during chemical reactions.
The discovery of relativistic effects in the lead-acid battery also sheds some light on why no corresponding “tin battery” exists. In the periodic table, tin is located directly above lead and has an atomic number of 50, making it lighter than lead. According to the scientists’ calculations, a tin battery would basically be a lead battery with very minimal relativistic effects. Although tin and lead have similar nonrelativistic energy values, tin’s small relativistic effects prohibit it from being used in an efficient battery.
Read the whole article here Car batteries powered by relativity.